diff options
| -rw-r--r-- | kernel/locking/lockdep.c | 43 |
1 files changed, 35 insertions, 8 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 78cd74d77be9..9160f1ddc435 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1838,10 +1838,37 @@ static inline bool class_equal(struct lock_list *entry, void *data) return entry->class == data; } +/* + * We are about to add B -> A into the dependency graph, and in __bfs() a + * strong dependency path A -> .. -> B is found: hlock_class equals + * entry->class. + * + * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong + * dependency cycle, that means: + * + * Either + * + * a) B -> A is -(E*)-> + * + * or + * + * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B) + * + * as then we don't have -(*R)-> -(S*)-> in the cycle. + */ +static inline bool hlock_conflict(struct lock_list *entry, void *data) +{ + struct held_lock *hlock = (struct held_lock *)data; + + return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */ + (hlock->read == 0 || /* B -> A is -(E*)-> */ + !entry->only_xr); /* A -> .. -> B is -(*N)-> */ +} + static noinline void print_circular_bug(struct lock_list *this, - struct lock_list *target, - struct held_lock *check_src, - struct held_lock *check_tgt) + struct lock_list *target, + struct held_lock *check_src, + struct held_lock *check_tgt) { struct task_struct *curr = current; struct lock_list *parent; @@ -1950,13 +1977,13 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class) * <target> or not. */ static noinline enum bfs_result -check_path(struct lock_class *target, struct lock_list *src_entry, +check_path(struct held_lock *target, struct lock_list *src_entry, + bool (*match)(struct lock_list *entry, void *data), struct lock_list **target_entry) { enum bfs_result ret; - ret = __bfs_forwards(src_entry, (void *)target, class_equal, - target_entry); + ret = __bfs_forwards(src_entry, target, match, target_entry); if (unlikely(bfs_error(ret))) print_bfs_bug(ret); @@ -1983,7 +2010,7 @@ check_noncircular(struct held_lock *src, struct held_lock *target, debug_atomic_inc(nr_cyclic_checks); - ret = check_path(hlock_class(target), &src_entry, &target_entry); + ret = check_path(target, &src_entry, hlock_conflict, &target_entry); if (unlikely(ret == BFS_RMATCH)) { if (!*trace) { @@ -2021,7 +2048,7 @@ check_redundant(struct held_lock *src, struct held_lock *target) debug_atomic_inc(nr_redundant_checks); - ret = check_path(hlock_class(target), &src_entry, &target_entry); + ret = check_path(target, &src_entry, class_equal, &target_entry); if (ret == BFS_RMATCH) debug_atomic_inc(nr_redundant); |